1. Field of the Invention
The present invention relates to a method for determining relative motion with the aid of a camera.
2. Description of the Related Art
It is already known to use an image recording system in a motor vehicle in order to obtain images of the vehicle's surroundings and, in combination with a driver assistance system, to facilitate the driving of the vehicle. An image recording system of this type includes at least one image sensor and one optical system associated with this image sensor, which maps a recorded field of the vehicle's surroundings onto the image sensor. The image sensor used in an image recording system of this type must process a broad range of different illumination levels in order to be able to deliver a usable output signal both in blazing sun and in poorly illuminated tunnels. While in the case of a conventional image sensor exposure sensitivity often follows a fixedly adjusted linear or logarithmic characteristics curve, image sensors have already been proposed (published German patent application document DE 103 01 898 A1 and published German patent application document DE 10 2006 027 121 A1) in which individual linear segments of this characteristics curve are individually adjustable. A characteristics curve of this type relates the absolute brightness of an object to the grayscale value in the image obtained from the object.
From the article “Velocity measurement based on image blur” by M. Celestiono and O. Horikawa in ABCM Symposium Series in Mechatronics, Vol. 3, pp. 633-642, 2008, it is furthermore known to measure the velocity of a vehicle over the ground in order to check the reliability performance of the tachometer. For this purpose, an image of the road segment traveled by the vehicle is detected by an image sensor which is integrated into the vehicle, and the detected image is compared with a previously recorded image. Velocity information is derived from the image blurred as a function of the velocity.